If you are a vegetarian, you may have noticed that you crave sweets. Not just sugar in your coffee, but sugary confections like pastries and candy. In The Vegetarian Myth, Lierre Keith, a former vegan, explains why that is so:

1. With the typical vegetarian diet, you are eating mostly carbohydrates and avoiding proteins (meat, fish, eggs, etc.). This almost certainly makes you hypoglycemic. You have frequent drops in your blood sugar levels. And that triggers a biologically based craving to get them back up.
2. The lack of protein also means your brain is starved of endorphins, which feed on protein. So your brain wants a health-damaging substitute: sugar. Sugar temporarily boosts endorphins by giving you an adrenaline rush.
3. Your brain also needs protein to produce tryptophan. Tryptophan produces serotonin. And without enough serotonin, you will feel depressed. Eating sugar temporarily boosts tryptophan.
4. A meat-poor diet robs you of energy. Once again, carbohydrates and sugar temporarily boost energy, only to deplete it later.